The present invention relates generally to automation control systems and, more particularly, to an automation system with integrated safe and standard control functionality.
Motion causing devices are commonly employed in a variety of environments including, for example, industrial facilities and construction environments. Such devices generally include a variety of different devices including, for example, motors and heating devices. There are circumstances in which such devices must be reliably disabled so as not to pose risks to human beings or other devices.
For example, motors often rotate at high speeds and/or provide significant torques that in certain situations could pose risks to human beings or other devices that come into contact with the motors themselves or with other devices coupled to those motors. In particular, when such motors or devices coupled to those motors are replaced, fixed, modified, tested or otherwise operated upon by human beings such as operators, engineers, or service technicians, it is desirable that the motors be reliably disabled such that the motors cease to rotate or deliver sustained torque.
In view of the possible hazards associated with automation equipment generally, many modern industrial and other facilities employ various electronic and other technologies that reduce the risk of accidents and enhance overall system safety. Additionally, standards have been developed with a goal of further reducing the risk of accidents. For example, with respect to industrial facilities, standards from organizations such as the ANSI, NFPA, ISO, CEN, CENELEC, and the IEC have been developed to establish requirements for safety. The technologies used to enhance system safety often are designed to comply with, or to assist in making a facility compliant with, standards from one or more of these organizations. Traditional safety system design has regarded the safety system as being separate from the machine control function. The safety system typically acts on its own with very little coordination with the standard control system.
In some situations frequent interactions between machinery and operators are expected. For example, a machine often performs one or more tasks on a single workpiece during a machine cycle. After the operation is complete, the workpiece is removed and a new workpiece is loaded into the machine. Operator intervention may be required to exchange the workpieces or position the new workpiece for processing. In other instances human interaction with the machine is less frequent and may occur during maintenance activities or commissioning. Regardless of the frequency of interaction, it is important that the machine control system provide for the safety of the workforce during both foreseen and unforeseen interactions. As machinery design advances and designers strive to complement human capabilities (e.g., flexibility, intelligent decision making) with those of machinery (e.g., strength, repeatability, tirelessness), these interactions become increasingly complex.
The operator load or unload function is an important interaction in that the frequency of exposure to potential hazards is high. This load operation may expose an operator to hazards at a frequency of greater than once per minute. Traditional control practice involves the standard control system placing the machine into the proper position or state of readiness for the operator load operation. The standard control system then prompts the operator to enter the hazardous area of the machine that is guarded by a light screen, floor mat or other safety sensing technology by turning on an indicator light or similar means of indicating the state of readiness of the machine. Although the machine has reached the proper state or position within its cycle, it has not yet achieved a state of safety readiness, because the operator has not yet broken the safety light curtain, floor mat or other safety protection device.
The act of the operator breaking the safety protection device puts the machine into a safe state by triggering the safety system. For instance, a typical safety system may include independent contactors that operate to isolate a motor or other machine from its source of power or drive signals. Other safety systems may interface with a motor drive to electrically disable the line drivers that generate the drive signals. Because the safety system is not triggered until after the safety protection device is activated, it is possible that the machine may not be placed in a safe state prior to the operator entering the hazardous area.
Therefore, it would be advantageous if a safety system could be integrated into the function of the overall control system to place the machine in the proper condition for the interaction (i.e., proper state or position) and be safety disabled before the operator is even prompted to enter the hazardous area.
This section of this document is intended to introduce various aspects of art that may be related to various aspects of the present invention described and/or claimed below. This section provides background information to facilitate a better understanding of the various aspects of the present invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.